Transpiratory cooling by expendable inserts



Sept. 2, 1969 C. H. MARTENS TRANSPIRATORY COOLING BY EXPENDABLE INSERTS Filed April 26, 1967 Charles H. Martens, INVENTOR. '"7

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United States Patent 3,464,208 TRANSPDRATORY COOLING BY EXPENDABLE INSERTS Charles H. Martens, Huntsville, Ala., assignor to the United States of America as represented by the Secretary of the Army Filed Apr. 26, 1967, Ser. No. 634,811 Int. Cl. F02k 1/22; B64d 33/04 US. Cl. 60265 1 Claim ABSTRACT OF THE DISCLOSURE A transpiratory cooling structure employing expendable inserts, which inserts have been previously introduced in a cavity or cavities within the walls of the bodies to be cooled. The use of such inserts in rocket nozzles and rocket guide vanes is illustrated herein.

BACKGROUND OF THE INVENTION This invention relates to the art of cooling the heated surfaces of bodies such as rocket nozzles, rocket guide vanes or re-entry bodies, and particularly to transpiratory cooling systems used in such bodies.

Prior art transpiratory cooling systems have been of the impregnation type, employing a method by which a body having a porous surface is cooled by the flow and/or evaporation of a coolant liquid through the porous surface from the interior. Film cooling at the interface results. This is also known as sweat cooling in the art.

These prior art impregnation-type systems have not been satisfactory, results have been unpredictable, cost has been high, and reliability has been low. Because of the nonuniform cellular structure of the porous body, duplicate results could not be obtained. The efiluence of the coolant could not be precisely located and controlled, and it was difficult to control the size and geometry of the impregnated body. Additionally, only certain limited types of liquid impregnants could be used.

Accordingly, a principal object of this invention is to provide an improved structure for transpiratory cooling.

Another object of this invention is to provide a structure for prolonged transpiratory cooling.

Still another object of this invention is to provide a structure for continuous transpiratory cooling.

Another object of this invention is to provide a structure for transpiratory cooling wherein results can be predicted and duplicated.

Another object of this invention is to provide a structure for transpiratory cooling wherein the eflluence of coolant can be precisely located and controlled.

Another object of this invention is to provide a structure for transpiratory cooling wherein the location of coolant can be predicted and controlled.

Another object of this invention is to provide a structure for transpiratory cooling wherein conventional fabrication techniques can be employed to assure end-product reliability and reduced costs.

Another object of this invention to to provide a structure for transpiratory cooling wherein a broad range of coolants, especially mixed and/ or stratified coolants, may be used.

SUMMARY OF THE INVENTION According to this invention, transpiratory cooling is effected through the use of expendable inserts, which inserts have been previously introduced in a cavity or cavities within the walls of the bodies to be cooled.

The novel features which are believed to be characteristic of this invention, together with further objects and advantages thereof, will be better understood from the following description considered in conjunction with the ac 3,464,208 Patented Sept. 2, 1969 "ice companying drawing, herein made a part of this specifica tion in which embodiments of this invention are illustrated by way of example. It is to be expressly understood, however, that the drawing is for the purpose of illustration and description only, and is not intended as a definition of the limits of this invention.

BRIEF DESCRIPTION OF THE DRAWING DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIGURE 1, there is illustrated a rocket 10 that includes a tubular or cylindrical casing 12 which is preferably of shrunk or welded slave construction to insure tight fit. The rear end of rocket 10 is provided with an axial opening 14 in which is positioned a rocket nozzle 16, the latter being secured to casing 12 in a conventional manner. Nozzle 16 is provided with an axial converging-diverging passage 18 which communicates at its inlet end with combustion chamber 20. Placed within cavities 21 in nozzle 16 are transpiratory cooling inserts 22.

Referring now to FIGURE 2, there is illustrated a guide vane 24. Placed with cavities 25, 27 and 29 in guide vane 24 are transpiratory cooling inserts 26, 28 and 30, respectively. Cavities 25, 27 and 29 are shown as being of different shapes; however, these different shapes in a single structure are not necessary and are simply a matter of the design of each guide vane. Transpiratory cooling insert 26 is shown made of stratified materials. This allows a cooling in stages of the guide vane.

The body whose heated surface is intended to be cooled may be a rocket nozzle as in FIGURE 1 of this invention, a rocket guide vane as in FIGURE 2, and a re-entry or other projected bodies exposed to an extremely high temperature environment. In the case of a rocket guide vane or re-entry bodies, the insert cavity opens to the outside surface of the body and leads directly to the surrounding atmosphere.

The transpiratory cooling inserts (22, 26, 28 or 30) of this invention are introduced during and/ or after the fabrication of the body whose heated surface is intended to be cooled. They are so arranged that part of the insert coincides with and terminates at or near the surface to be cooled. The remainder of the insert is included within the body.

When the surface in which the transpiratory heating insert terminates is heated, the insert is caused to be melted and thereafter forced out by vaporization. The melting of the cooling insert originates at or near the heated surface at which one end of the insert terminates. The insert is designed to melt at a temperature lower than the melting or functionally destructive temperature of the heated surface and the adjacent segments of the body. The melting of the inserts causes liquid and/or gas to flow through the body openings which terminate at the heated surface. This passing of liquid and/ or gas to the exterior of the body causes heated surface and adjacent body cooling by one or more of the methods of vaporization, radiation, conduction and convection.

Frequently used insert materials are lithium, tin, copper, lead, aluminum, silver, gold and many plastics. Lithium is an especially desirable material (if otherwise proper from a design viewpoint) because of its high heat of vaporization. Other solid or semisolid materials should be considered in the choice of an insert material. Accordingly,

3 the term solid is herein defined to include a semisolid material.

The transpiratory cooling inserts may be made of homogeneous, mixed and/or stratified (layers) materials. They may be arranged, as desired, in regular or irregular patterns.

The transpiratory cooling inserts may be placed in the body to be cooled during the process of manufacture. For example, transpiratory cooling rods may be placed during fabrication in a fiber-matrix nozzle. Another method of placing the transpiratory cooling inserts is the location of the inserts in holes within the body. These holes, whose exact dimensions may be predetermined, may be drilled, cored, pressed or otherwise introduced into the body. A hole and its contained transpiratory cooling insert may be, as desired, either of uniform or nonuniform size and shape within the body. If desired, a transpiratory cooling passage may connect within the body to a coolant reservoir, thus permitting a prolonged coolant activity. A transpiratory cooling insert may be introduced in a hole by infabrication or post-fabrication pressing, injection or other means. A hole and/or its insert may be so fabricated by serrating or shaping so that the insert is unlikely to leave the cavity in other than a liquid and/ or gaseous state.

Whichever method is used for introducing the inserts, the cavities for the cooling inserts, regardless of size and shape, have one end terminating at the surface to be cooled. The other end or ends of the cooling insert holes may be made blind by any desired method.

In FIGURE 1, when the motor of rocket 12 is ignited, hot gases from the motor are expended through the rocket nozzle, and inserts 22 are melted to effect cooling of the nozzle.

In FIGURE 2, when the guide vane is subjected to hot gases by passing through the atmosphere at high speeds, inserts 26, 28 and 30 are melted to effect cooling of the nozzle.

Obviously, many modifications and variations of this invention are possible in the light of the above teachings.

It is, therefore, to be understood that this invention may be practiced otherwise than as specifically described.

I claim:

1. A unitary rocket nozzle insert having a convergingdiverging axial passage therethrough, said converging-diverging axial passage defining a continuous surface subjected to hot gases, said nozzle insert having a plurality of cavities formed therein, each said cavity terminating at said surface; and means for cooling said nozzle insert at said surface comprising solid coolant material having a melting point substantially lower than the melting point of said nozzle insert, said coolant material comprising layers of different coolant materials disposed within and completely filling each of said cavities, said coolant material having a surface which coincides with and terminates at said surface of said nozzle insert to form a continuous portion thereof, whereby, when said hot gases flow over said surface of said nozzle insert and melt said coolant material, said nozzle insert will be cooled.

References Cited UNITED STATES PATENTS 3,014,353 12/1961 Scully 200 3,026,806 3/1962 Runton 60-200 3,115,746 12/1963 Hsia 60-271 3,122,883 3/1964 Terner 60-200 3,137,998 6/1964 Beam 60-265 3,248,874 5/1966 Grina 239-265.15 3,251,554 5/1966 Kraus 239-26515 3,267,857 8/1966 Lindberg 102-105 3,282,421 11/1966 Prosser 239265.l5 3,338,687 8/1967 Dickinson 239-265.15

CARLTON R. CROYLE, Primary Examiner DOUGLAS HART, Assistant Examiner U.S. Cl. X.R. 

